Tire having carcass cords describing s-shaped and z-shaped paths

ABSTRACT

The carcass reinforcement of a pneumatic tire extends continuously from one bead wire to the other. The cords of the reinforcement have a substantially longitudinal orientation under the tread portion, an oblique orientation between the midpoint of each sidewall and the corresponding bead wire, and, between the midpoint of each sidewall and the corresponding shoulder, an Sshaped path tangent at two circumferentially and radially separated points to radial planes of the tire.

[ Jan. 1,1974

United States Patent [191 Boileau TIRE HAVING CARCASS CORDS ReferencesCited UNITED STATES PATENTS DESCRIBING S-SHAPED AND Z-SHAPED PATHS [75]Inventor:

Jacques Boileau, Clermont-Ferrand, 3,605,849Boileau........................... 152/356 Fr 3,581,793 6/1971 Wittneben152/354 FOREIGN PATENTS OR APPLICATIONS [73] Assignee: CompagnieGenerale Des 992,341 5/1965 Great Britain...................... 152/354Establissements Michelin, raison mm ma Hu m m 0U r. YB m. DM e am V mn XE. WW m m "t PA a m 0 e new i CW &d .mm Mm F l n- W e e C Mmn chm mCF[57] ABSTRACT The carcass reinforcement of a pneumatic tire extends [22]Filed: Oct. 15, 1971 21 Appl. No.: 189,657

continuously from one bead wire to the other. The

30 Foreign Application priority Data cords of the reinforcement have asubstantially longioct 19 1970 tudinal orientation under the treadportion, an oblique July 30, 1971 France..........................7037730 orientation between the midpoint of each sidewall and thecorresponding bead wire, and, between the mid- France point of eachsidewall and the corresponding shoulder, an S-shaped path tangent at twocircumferentially and radially separated points to radial planes of thetire.

[52] US. [51] Int. [58] Field of Search..,........

152/359 10 Claims, 8 Drawing Figures PATENTED JAN 1 I974 SHEET 2 BF 4FIG. 3

TIRE HAVING CARCASS CORDS DESCRIBING S-SIIAPED AND Z-SIIAPED PATHSBACKGROUND OF THE INVENTION This invention relates to pneumatic tiresfor automotive vehicles and, more particularly, to novel andhighly-effective pneumatic tires having an improved reinforcement and toa method of making the tires.

Two main types of tires which differ in the structure of theirreinforcement are at present being produced: the bias tire and theradial tire.

In the bias tire the carcass is composed of cords arranged diagonally intwo symmetrical directions. It is possibly supplemented by a treadreinforcement consisting of oblique cords parallel or approximatelyparallel to those of the carcass.

In the radial tire the carcass is composed of cords ar ranged in radialplanes and it is reinforced by a tread reinforcement which makes thetread undeformable parallel to its surface and comprises cords arrangedalong directions which do not substantially differ from the longitudinaldirection.

With regard to manufacture, tires with a bias carcass are much easierand cheaper to manufacture than tires with a radial carcass. The mainreason is that they require the assembling of a smaller number of partsand call for less precision in assembling.

With regard to the properties, on the other hand, the balance isdefinitely in favor of the radial tire, which provides in particularmuch greater safety'and longer life. Despite its higher cost, the radialtire is, in the long run, much more economical. However, the bias tirehas certain advantagesin addition to ease of manufacture, mention may bemade of the strength of the sidewalls and better absorption of shocks.

Of course, many attempts have been made to effect a combination of theadvantages of the two types of tires. Most have led only to compromiseswhich result in a loss of both the great simplicity of manufacture ofthe bias tire and the excellent properties of the radial tire. Onewell-known attempt is that which relates to the so-called bias-belted"structure, that is to say a belted bias tire; this is more expensive toproduce than the conventional bias tire and moreover is far inferior tothe radial tire in its qualities. Of the attempts directed at a trulyoriginal structure, the most interesting is the one described in mycopending divisional US. Pat. application Ser. No. 124,831, filed Mar.3, 1971, and its parent application Ser. No. 795,759, filed Nov. 13,1968, and issued on Sept. 20, 1971, as US. Pat. No. 3,605,849. Thisstructure comprises the use of cores which are continuous from steelbead wire to steel bead wire but have different orientations indifferent regions of the tire: namely, approximately longitudinal underthe tread, radial in a region between the shoulder and the midpoint ofthe sidewall, and oblique between the midpoint of the sidewall and thebead. Because of the use of special cord plies in which the cords arebiased over the major part of the width of the ply and are perpendicularto the edges over short regions, such a tire is also manufactured moreeasily than a bias tire. This tire furthermore has properties which makeit much more similar to the radial tire than to the bias tire, althoughits structure is closer to that of the bias tire.

SUMMARY OF THE INVENTION An object of the invention is to remedy theproblems of prior-art tires noted above and to improve the structuredisclosed in application Ser. No. 124,831 mentioned above. Inparticular, an object of the invention is to provide a tire which,unlike conventional tires, affords the possibility of angulardisplacement of the tread with respect to the sidewalls, which improvesthe behavior of the tire. Another object is to permit easy andeconomical manufacture from plies produced with acceptable tolerances.

The foregoing and other objects are attained in accordance with theinvention by the provision of a tire comprising a reinforcement made ofcords which are continuous from steel bead wire to steel bead wire andwhich have different orientations in different regions of the tire andin particular an approximately longitudinal orientation under the treadand an oblique orientation between the midpoint of each wall and thecorresponding steel bead wire. The tire is characterized in that thecords, between the midpoint of each wall and the corresponding shoulder,have an S-shaped or Z-shaped path which is tangent at two points to theradial planes of the tire.

Preferably, the distance in the radial direction between the points oftangency of one and the same cord with the radial planes is betweenone-sixth and onethird of the height of the sidewall. It is ideallyclose to one-quarter of such height and extends approximately over halfthe distance between the center point of the sidewall and the shoulder.

In one embodiment, the cords of the same ply are contiguous under thetread. In another embodiment, the cords rise again up to the height ofthe middle of the sidewalls after having passed around the steel beadwires.

In another embodiment of the invention, the reinforcement, as definedabove, is supplemented by a tread reinforcement extending substantiallyunder the entire width of the tread and comprising at least two plies ofcords slightly inclined to the longitudinal direction and beingcrosswise from ply to ply.

The tire is preferably characterized by the following additionalfeatures:

a. The angle made by the cords of the tread reinforcement with thelongitudinal direction of the tire is smaller than that made by thecords which continue from steel bead wire to steel bead wire and formthe carcass reinforcement;

b. between the tread reinforcement and the carcass reinforcement, alayer of soft rubber is interposed; and

c. the change in direction of the cords of the carcass reinforcementcommences at a point below the tread reinforcement so that the portionof the cords having an S-shaped path partially overlaps the treadreinforcement.

The presence of the tread reinforcement reduces the relatively largeshearing forces between the plies of the carcass reinforcement in theregion of the shoulders of the wire.

The method of manufacturing tires in accordance with the invention whichdo-not have a tread reinforcement comprises the steps of assembling on atiremaking drum superimposed plies of cords which are continuous fromsteel head wire to steel bead wire and arranged along severaldirections, placing a tread on the carcass which has thus been formed,and shaping the unit thus prepared and vulcanizing it in a mold. The

method is characterized in that the plies comprise cords arrangeddiagonally along a first direction in the major part of their length andalong the opposite direction in two intermediate zones.

Preferably, the angle of the cords in the intermediate zones of theplies is symmetrical (of equal magnitude and opposite signs as referredto the longitudinal direction of the tire) with the angle of the cordsin the other zones and in any case does not differ by more than from thesymmetrical angle. The angles of the different portions of one and thesame cord with the edge of the ply are between 40 and 55. Theircenter-to-center spacing e is close to:

e d/t VI cos a /I (t cos d in which d is the diameter of the cords, dtheir angle of lay with respect to the longitudinal direction of thetire and t the conformation ratio, thatis to say the ratio of thediameter of the tread to that of the steel bead wires of the tire. For avalue of n close to 50 and a value of r close to 1.5, the spacing isclose to 2d.

The presence in the tire of the invention of a zone between eachshoulder and the midpoint of the sidewall which is reinforced with cordswhich are not radial but form greatly elongated intersecting Ss has theremarkable property of imparting to the tread a certain freedom torotate with respect to the sidewalls. This reduced circumferentialrigidity results in increased comfort and, surprisingly, increasedsafetythe sidewalls pull less on the tread, which thus remains flatteron the ground.

With regard to manufacture, experience shows that the process of theinvention easily and without drawback tolerates irregularities inmanufacture of the plies-the portion of the reinforcement in which thecords are only slightly inclined to the radial planes is put in placemore easily and with more uniformity when such portion has been obtainedby a change in direction of the cords than when the cords are initiallyplaced radially. Manufacturing irregularities frequently result in anS-shaped path which is slightly variable, depending upon the cords. Theimportant factor is that all the cords have an S-shape; the preciseshape of the S is of less importance.

The tire in accordance with the invention which has both a carcassreinforcement and a tread reinforcement can be made in two sets ofsteps, the first comprising the manufacture and shaping of the carcass,and the second comprising the placing on of the tread reinforcement andof the tread. However-and this also constitutes a characteristic of theinvention, one can perform the steps in a different order by, forexample, superimposing the carcass, the tread reinforcement and thetread on a tire-making drum and then proceeding with the shaping and thevulcanizing. The tread reinforcement then permits good centering of thetire in the vulcanization press, by physically representing the centerplane of the tire and avoiding asymmetry with respect to the centerplane. It is, however, desirable to place a layer of soft rubber betweenthe carcass reinforcement and the tread reinforcement in order to makethe tire conformable. Furthermore, the angle between carcass cords andtread reinforcement cords should not exceed and preferably 15.

BRIEF DESCRIPTION OF THE DRAWING An understanding of other aspects ofthe invention can be gained from a consideration of the followingdetailed description of the preferred embodiments thereof, inconjunction with the appended figures of the drawing, wherein:

FIG. 1 is a side elevational perspective view of a portion of a tire inaccordance with the invention, the rubber of the sidewalls and of thetread being partly broken away;

FIG. 2 is a top plan view of the same section of tire;

FIGS. 3 and 4 are views on a smaller scale, in section and in developedplan, respectively, of the reinforcement plies of the tire of FIGS. 1and 2 when arranged on a tire-making drum;

FIG. 5 is a top plan view of a portion of tire with tread reinforcement,the rubber being broken away;

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a tire Ihaving a tread 2 provided with grooves 3 and extended by two sidewalls 4which are terminated by beads 5 containing steel bead wires 6. Themiddle of the sidewall 4, corresponding to the region of maximum width,is marked by a circular band 7. The shoulder, that is to say the zone ofmaximum meridian curvature, is also marked by a circular band 8. Anothercircular band 9 indicates the junction of the sidewall and the bead.

The reinforcement of the tire is composed solely of two plies l0 and 11,one shown in solid lines (ply 11) and the other in dashed lines (ply10). For clarity in the drawing, only one cord out of about eight hasbeen shown. The cords of these plies extend continuously from one steelhead wire 6 to the other. They move around each steel bead wire 6 andtheir ends are located substantially at the level of the band 7, that isto say, at the midpoint of the sidewall 4.

The cords of the plies l0 and 1 l have special orientations in threeregions. First of all, as shown in FIG. 2, below the tread 2, they areslightly inclined to the longitudinal direction XX; the angle a in thisregion is Between the midpoint of the sidewall 4 and the steel bead wire6, the cords of the plies 10 and I1 and of their return portions formangles of the order of 45 to 50 with the steel bead wire 6 or with theparallel circles of the tire. Between the sidewall midpoint 7 and theshoulder 8, the cords of the plies l0 and 1 l have respectively, inaccordance with the invention, a very characteristic S-shaped orZ-shaped path which is tangent at two points, such as 14 and 15, to theradial planes Y-Y' and 2-2.

In accordance with the invention, the angular distance between theradial planes Y--Y' and Z-Z' is within the range of one to five timesthe angular distance between corresponding points of adjacent cords. Inthe case of the structure of FIGS. 1 and .2, the angular distancebetween the radial planes YY and 2-2 is approximately twice the angulardistance between corresponding points of two successive cords of thesame ply.

The distance in radial direction between the points 14 and 15 isapproximately equal to one-half the radial distance between the sidewallmidpoint 7 and the shoulder 8.

FIGS. 3 and 4 give characteristics of manufacture which have made itpossible to obtain the tire of the invention shown in FIGS. 1 and 2 insize 165-15.

These figures show the two plies l0 and 11 arranged, together with thetwo steel bead wires 6, on a tiremaking drum 20. Each ply has a centralportion 22, two narrow intermediate zones 23 (shown in dotted line inFIG. 3), two lateral zones 24 and two return portions 25. The dimensionsof these different zones are given in millimeters in FIG. 3. The anglesmade by the cords with the longitudinal direction are indicated in FIG.4; in absolute value, these angles are all equal to 51, this being truealso in the intermediate zones 23 and in the return portions 25. In thecase of each ply, however, the directions of the angles are opposite inzones 22 and 24 on the one hand and 23 and 25 on the other hand. Theangle in the zones 23 can differ from 51 by to without this leading toany fundamentally different result. However, it is preferable that thisangle be as close as possible to the angle in the other zones. On thecarcass which has thus been produced, it is sufficient to place a treadand the covering of the sidewalls and then to give the unit a toricshape and vulcanize it in a mold in order, to obtain the tire of FIGS. 1and 2.

By way of illustration, the cords used are 1100/3 polyester threads. Thedistance between the threads is 1.8 mm and their diameter close to 0.7mm, which has the result that the threads are practically contiguousunder the tread. The thickness of the calendering is 0.27 mm on eachside of the plies, the rubber used having a Shore hardness of 82 and amodulus of elasticity of 39 kg/Em' 21("100 pe rcent elong ation. Thecuring mold used has in the example a diameter at the tread of 618 mmand an inner axial width of 166 mm at the height of the band 7.

Under these conditions, the following table gives the side thrust of thetire inaccordance with the invention E compared with that of twocommercial control tires T and T, both of radial type, one having areinforcement entirely of textile and the other having a carcass oftextile and a tread reinforcement of metal cables.

Drift Angle Side thrust in kg (wheel 4% .I 15

Pressure 2.0 bars Tire load 450 kg) E T T' (textile) (metal) 2 122 1 I8I46 Evidently, tire E is markedly superior to the alltextile radialtire. Moreover, its side thrust increases more rapidly with an increasein the angle of drift than does the side thrust of a radial tire havinga metal tread reinforcement. Nevertheless, it is not a radial tire.

In order to obtain plies such as the plies 10 and 11 in which thediagonal cords are, in two intermediate zones, inclined at an anglesymmetrical with respect to the angle of inclination of the portions ofthe cords immediately adjacent to the intermediate zones, one can use inpart the process described in my copending Pat. application Ser. No.795,759 now US. Pat. No. 3,605,849 referred to above. This processincludes producing a relative displacement of the central portion 22with respect to the lateral portions 24 and return portions 25 in orderto modify the inclination of the cords in the intermediate portions 23.It is not necessary to obtain in these intermediate portions 23 an angleexactly symmetrical with respect to that of the portions 22 and 24;however, it is preferable to approach a symmetrical angle as closely aspossible. The symmetrical angle is in fact the smallest angle with thelongitudinal direction which is stable; with a smaller angle, thedeformation is not stable, since, as a result of a reduction in thedistance between cords, it leads to compression of the calenderingrubber; with a larger angle, the advantages obtained by the inventionare reduced.

FIGS. 5 and 6 show a tire I having a tread 2 provided with grooves 3 andextended by two sidewalls 4 terminating in beads 5 containing steel beadwires 6.

The reinforcement of the tire comprises two carcass plies 10 and 11 andtwo tread plies 30 and 31.

The cords of the carcass plies l0 and 11 are inclined with respect tothe longitudinal direction by an angle of 39 between the lines AA' andB-B' located some distance from the edges of the tread plies 30 and 31.Between the line A-A' or 8-8 and the midpoint of the sidewall which isphysically indicated by the band 7, the cords of the plies 10 and 11have an S-shaped course. Between the sidewall midpoints 7 and the steelbead wires 6, the cords of the plies 10 and 11 or their return portionsaround the steel head wires form an angle of about 45 to 50.

The cords of the tread plies 30 and 31 are inclined with respect to thelongitudinal direction by an angle of 21.

The carcass plies l0 and 11 and the tread plies 30 and 31 are separatedfrom each other by a layer of relatively soft rubber 32.

FIGS. 7 and 8 show the construction characteristics which make itpossible to obtain the tire of FIGS. 5 and 6 in size l380.

These figures show the two carcass plies l0 and 11 and the two treadplies 30 and 31 arranged together with the two steel bead wires 6, onthe tire-making drum 20.

Each carcass ply 10 or 11 comprises a central portion 22, twointermediate portions 23 shown in dashed lines in FIG. 7, two lateralzones 24 and two return portions 25. The dimensions of these differentzones are given in millimeters in FIG. 7. The angles of the cords of theplies l0 and 11 are given in FIG. 8; the inclination of these cords tothe longitudinal direction is 60 in portions 22, 24 and 25 and inportions 23.

Each tread ply 30 or 31 is composed of cords inclined by an angle of 46,as shown in FIG. 8. The width of these plies is given in millimeters inFIG. 7.

Between the plies 10 and 11 on the one hand and the plies 30 and 31 onthe other hand there is arranged a layer of soft rubber 32 of a widthgreater than that of the plies 30 and 31. Furthermore, covering theintermediate portions 23 there are arranged two bands of soft rubber 33.

By way of illustration, the cords used for the plies 10 and 11 are of l/3 polyester yarns. The distance between the cords is 1.4 mm. Thethickness of the calendering is 0.4 mm on each side, the calenderingrubber having a modulus of 1 l5 kg/cm at 100 percent elongation. Thecords used for the plies 30 and 31 are steel cables comprising fourwires of 0.23 mm diameter. The distance between these cables is 1.6 mm.The thickness of the calendering is 0.4 mm, the calendering rubberhaving a modulus of 390 kg/cm at 100 percent elongation. The rubber ofthe layers 32 and 33 has a modulus of 115 ltg/cm at 100 percentelongation. Their thicknesses are 0.6 and 0.8 mm respectively. Underthese conditions, the drift thrust of the tire of FIGS. 5 to 8 is 126.5kg with 2 drift and 454.5 kg with drift, for an inflation pressure of2.0 bars and a load on the tire of 450 kg, and with a wheel of type 4% Jl5. Moreover, the tire in accordance with the invention clearly differsfrom a bias-belted tire manufactured with the same components. Inparticular, under a load of 450 kg and an inflation pressure of 2 bars,it has a crushing deflection of more than 6 mm due to the fact that thecords of the carcass have an S-shaped path tangent to the radial planesof the tire in the vicinity of the shoulders. This results in aconsiderable increase in comfort.

The special plies of the invention described above are of courseindependent of the process used to obtain them.

Thus there are provided in accordance with the invention a novel andhighly effective pneumatic tire having an improved reinforcement and amethod of making the tire. Many modifications of the embodimentsdescribed herein will readily occur to those skilled in the art uponconsideration of this disclosure. For example, it is within the scope ofthe invention to form, instead of an S-shaped path having a singlecycle, an undulated path having more than one or a plurality of cycles.ln particular, one may employ plies having zones formed of zigzag cords.Accordingly, the invention is to be construed as including all theembodiments thereof within the scope of the appended claims.

I claim:

1. A tire comprising a tread portion, a pair of sidewalls respectivelyextending radially inwardly from opposite edges of said tread portionand respectively joining said tread portion at a pair of shoulders, eachsidewall having a bead at the radially inward edge thereof, each beadhaving therein a bead wire, and a carcass reinforcement, saidreinforcement being formed of an even number of plies continuous fromone of said bead wires to the other, each of said plies comprisingparallel reinforcement cords which assume different orientations indifferent regions of the tire and which have an orientation below thetread only slightly inclined to the longitudinal direction, an obliqueorientation between the midpoint of each sidewall and the correspondingbead wire, and, in a region between the midpoint of each sidewall andthe corresponding shoulder, a reverse inclination opposite to theinclination of portions of the same ply that are radially outward andradially inward of said region, so that said plies are respectivelyS-shaped and Z-shaped, each cord of each ply is tangential at twodifferent points to two different radial planes of the tire, and thecords of one ply intersect corresponding cords of the other at threepoints.

2. A tire according to claim I wherein said reinforecement cords arecontiguous in said tread portion.

3. A tire according to claim 1 wherein said reinforcement cords extendaround said bead wires and rise again in each sidewall substantially tothe midpoint thereof.

4. A tire according to claim 1 further comprising a tread reinforcementsubstantially coextensive with said tread portion and comprising atleast two plies of cords, the cords of said tread plies being slightlyinclined with respect to the longitudinal direction of the tire and thecords of each of said tread plies being in crossed relation with respectto the cords of the other of said tread plies.

5. A tire according to claim 1 further comprising a tread reinforcementsubstantially coextensive with said tread portion and comprising atleast two plies of cords, the cords of each of said tread plies being incrossed relation with respect to the cords of the other of said treadplies and the cords of both of said tread plies forming with thelongitudinal direction of the tire angles smaller than those formed withthe longitudinal direction of the tire by said reinforcement cords undersaid tread portion.

6. A tire according to claim 1 further comprising a tread reinforcementsubstantially coextensive with said tread portion and comprising atleast two plies of cords, the cords of said plies being slightlyinclined with respect to the longitudinal direction of the tire and thecords of each of said tread plies being in crossed relation with respectto the cords of the other of said tread plies, further comprising alayer of soft rubber separating said carcass reinforcement from saidtread reinforcement.

7. A tire according to claim 1 further comprising a tread reinforcementsubstantially coextensive with said tread portion and comprising atleast two plies of cords, the cords of said tread plies being slightlyinclined with respect to the longitudinal direction of the tire and thecords of each of said tread plies being in crossed relation with respectto the cords of the other of said tread plies and wherein said reverseinclination is located partly below said tread reinforcement.

8. A tire comprising a tread portion, a pair of sidewalls respectivelyextending radially inwardly from opposite edges of said tread portionand respectively joining said tread portion at a pair of shoulders, eachsidewall having a bead at the radially inward edge thereof, each beadhaving therein a bead wire, and a carcass reinforcement, saidreinforcement comprising cords which are continuous from one of saidbead wires to the other and which have a substantially longitudinalorientation under said tread portion, an oblique orientation between themidpoint of each sidewall and the corresponding bead wire, and, betweenthe midpoint of each sidewall and the corresponding shoulder, an S-shaped path tangent at two points to radial planes of the tire, theangular distance between said points of tangency to a given cord beingwithin the range of one to five times the angular distance betweencorresponding points of adjacent cords.

9. A tire comprising a tread portion, a pair of sidewalls respectivelyextending radially inwardly from opposite edges of said tread portionand respectively joining said tread portion at a pair of shoulders, eachsidewall having a bead at the radially inward edge thereof, each headhaving therein a bead wire, and a carcass reinforcement, saidreinforcement comprising cords which are continuous from one of saidbead wires to the other and which have a substantially longitudinalorientation under said tread portion, an oblique orientation between themidpoint of each sidewall and the corresponding bead wire, and, betweenthe midpoint of each sidewall and the corresponding shoulder, an S-shaped path tangent at two points to radial planes of the tire, theradial distance between said points of tangency to "a given cord beingwithin the range of onesixth to one-third of the radial height of one ofsaid sidewalls.

orientation under said tread portion, a oblique orientation between themidpoint of each sidewall and the corresponding bead wire, and, betweenthe midpoint of each sidewall and the corresponding shoulder, an S-shaped path tangent at two points to radial planes of the tire, theradial distance between said points of tangency to a given cord beingsubstantially one-quarter of the radial height of one of said sidewalls.

Col. 1, line 51, "cores" should read --cords--; C01. 3, line 6 PO-{OBOUNITED STATES PATENT- OFFICE CERTIFICATE OF CORRECTION Patent No.3,782,441 Dated Jgggry l, 1974 Inyenror(s) Jacques Boileau It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

"conformable" should read --b1ank easy to shape--; Col. 6, line 35,after "165-380" insert (Eur0pean size)--; Col; 7, lines 56 and 57,"reinforecement" should read reinforcement-; and Col. 10, line 1, "a"should read --an--.

Signed and sealed this 24th day of September.1974.

(SEAL) Attest: I

fmccoy M. GIBSON JR. c. MARSHALL'DANN Attesting Officer Commissioner ofPatents

1. A tire comprising a tread portion, a pair of sidewalls respectivelyextending radially inwardly from opposite edges of said tread portionand respectively joining said tread portion at a pair of shoulders, eachsidewall having a bead at the radially inward edge thereof, each beadhaving therein a bead wire, and a carcass reinforcement, saidreinforcement being formed of an even number of plies continuous fromone of said bead wires to the other, each of said plies comprisingparallel reinforcement cords which assume different orientations indifferent regions of the tire and which have an orientation below thetread only slightly inclined to the longitudinal direction, an obliqueorientation between the midpoint of each sidewall and the correspondingbead wire, and, in a region between the midpoint of each sidewall andthe corresponding shoulder, a reverse inclination opposite to theinclination of portions of the same ply that are radially outward andradially inward of said region, so that said plies are respectivelyS-shaped and Z-shaped, each cord of each ply is tangential at twodifferent points to two different radial planes of the tire, and thecords of one ply intersect corresponding cords of the other at threepoints.
 2. A tire according to claim 1 wherein said reinforecement cordsare contiguous in said tread portion.
 3. A tire according to claim 1wherein said reinforcement cords extend around said bead wires and riseagain in each sidewall substantially to the midpoint thereof.
 4. A tireaccording to claim 1 further comprising a tread reinforcementsubstantially coextensive with said tread portion and comprising atleast two plies of cords, the cords of said tread plies being slightlyinclined with respect to the longitudinal direction of the tire and thecords of each of said tread plies being in crossed relation with respectto the cords of the other of said tread plies.
 5. A tire according toclaim 1 further comprising a tread reinforcement substantiallycoextensive with said tread portion and comprising at least two plies ofcords, the cords of each of said tread plies being in crossed relationwith respect to the cords of the other of said tread plies and the cordsof both of said tread plies forming with the longitudinal direction ofthe tire angles smaller than those formed with the longitudinaldirection of the tire by said reinforcement cords under said treadportion.
 6. A tire according to claim 1 further comprising a treadreinforcement substantially coextensive with said tread portion andcomprising at least two plies of cords, the cords of said plies beingslightly inclined with respect to the longitudinal direction of the tireand the cords of each of said tread plies being in crossed relation withrespect to the cords of the other of said tread plies, furthercomprising a layer of soft rubber separating said carcass reinforcementfrom said tread reinforcement.
 7. A tire according to claim 1 furthercomprising a tread reinforcement substantially coextensive with saidtread portion and comprising at least two plies of cords, the cords ofsaid tread plies being slightly inclined with respect to thelongitudinal direction of the tire and the cords of each of said treadplies being in crossed relation with respect to the cords of the otherof said tread plies and wherein said reverse inclination is locatedpartly below said tread reinforcement.
 8. A tire comprising a treadportion, a pair of sidewalls respectively extending radially inwardlyfrom opposite edges of said tread portion and respectively joining saidtread portion at a pair of shoulders, each sidewall having a bead at theradially inward edge thereof, each bead having therein a bead wire, anda carcass reinforcement, said reinforcement comprising cords which arecontinuous from one of said bead wires to the other and which have asubstantially longitudinal orientation under said tread portion, anoblique orientation between the midpoint of each sidewall and thecorresponding bead wire, and, between the midpoint of each sidewall andthe corresponding shoulder, an S-shaped path tangent at two points toradial planes of the tire, the angular distance between said points oftangency to a given cord being within the range of one to five times theangular distance between corresponding points of adjacent cords.
 9. Atire comprisiNg a tread portion, a pair of sidewalls respectivelyextending radially inwardly from opposite edges of said tread portionand respectively joining said tread portion at a pair of shoulders, eachsidewall having a bead at the radially inward edge thereof, each beadhaving therein a bead wire, and a carcass reinforcement, saidreinforcement comprising cords which are continuous from one of saidbead wires to the other and which have a substantially longitudinalorientation under said tread portion, an oblique orientation between themidpoint of each sidewall and the corresponding bead wire, and, betweenthe midpoint of each sidewall and the corresponding shoulder, anS-shaped path tangent at two points to radial planes of the tire, theradial distance between said points of tangency to a given cord beingwithin the range of one-sixth to one-third of the radial height of oneof said sidewalls.
 10. A tire comprising a tread portion, a pair ofsidewalls respectively extending radially inwardly from opposite edgesof said tread portion and respectively joining said tread portion at apair of shoulders, each sidewall having a bead at the radially inwardedge thereof, each bead having therein a bead wire, and a carcassreinforcement, said reinforcement comprising cords which are continuousfrom one of said bead wires to the other and which have a substantiallylongitudinal orientation under said tread portion, a oblique orientationbetween the midpoint of each sidewall and the corresponding bead wire,and, between the midpoint of each sidewall and the correspondingshoulder, an S-shaped path tangent at two points to radial planes of thetire, the radial distance between said points of tangency to a givencord being substantially one-quarter of the radial height of one of saidsidewalls.